The development of weak spots or leaks in tubular members in locations not accessible to repair, such as in subsea wellheads, creates serious repair problems. When such repairs are needed in a well casing string, it has been the practice to cut the casing in the well bore below the bad spot, removing the upper cut portions of the casing string,installing a packer type of patch by slipping it over the permanent part of the casing string and securing it to the casing string and then reconnecting good casing to the patch to complete the casing string.
Another method includes removing the casing above the damaged or bad area, lowering an overshot type of casing patch having a lower bowl carrying a spiral grapple into surrounding relation to the upper portion of the casing in the well bore, and engagement of the patch with the casing is followed by lifting the string to compress the lead to form a highly effective seal between the casing and the patch.
Another solution which has been proposed is to provide an internal steel tubing covered with a glass mat and epoxy resin. When set, the corrugated patch expands radially to conform symmetrically to the casing bore. Also, it is claimed that the epoxy resin extrudes into cavities in the tubing or casing wall to act as a gasket and sealing agent.
Still another solution which is disclosed in U.S. Pat. No. 2,495,352 is to remove the string above a break and lower another string which has an enlarged lower end into surrounding relationship to the upper end of the broken string in the well. A plastic material is pumped down the new string with a plug set into the top of the broken string so that the plastic is diverted into the annulus between the enlarged lower end and the upper end of the broken string and also around the exterior of the enlarged lower end. The setting of the plastic provides an uninterrupted bore extending through the lower broken string, through the set plastic and into the upper string.
It has been known to utilize internal pressure to form a first tubular member placed within a second tubular member having internal grooves so that the first tubular member is deformed into such grooves to provide a positive seal and also to join the two tubular members. Examples of this type of joint forming are shown in U.S. Pat. Nos. 4,388,752; 4,330,144; 2,438,529; 2,477,676; and 3,432,916. U.S. Pat. No. 4,593,448 discloses the use of half rings of collapsible material positioned within the grooves of the outer members when the forming is to be done under water. The function of the material is to permit forming which would otherwise be limited or prevented by the entrapment of water in the grooves. Also, it avoids the obvious solution of porting the grooves to the exterior of the second tubular member which avoids entry of water or other materials which could limit the useful life of the formed joint.